32 Proceedings of the Royal Irish Academy. 



type specimens of Ellisella, and compared them with authentic species of 

 Scirpearia, and could find no reason for separating them. 



Hickson (xv, pp. 818-819), in his vahiable contribution to the study of this 

 group, has suggested the abolition of the genus Ellisella and has united the 

 species included under that name to those of the genus Juncella. He, 

 however, divides the species so included into two groups — (1) those with clubs 

 and (2) those without clubs, the former of which, as will be evident, 

 corresponds to Juncella; and the latter, with the exception of J. spiralis, 

 which will be discussed later, to Ellisella as defined by their spiculation. 



The result of this is that the genus Juncella, which was distinguished by 

 the presence of the clubs amongst its spicules, now includes forms whose 

 spiculation is identical with that of Scirpearia and Scirpearella. 



The question now resolves itself into, " How are we to distinguish 

 between (1) those species of Juncella whose spicules contain no clubs, 

 (2) Scirpearia, and (3) Scirpearella?" In other words, we have still to find 

 generic characters and separate Ellisella, Scirpearia, and Scirpearella. 



As the result of an examination of all the type species of Ellisella, 

 Scirpearella, and Scirpearia (with the exception of *S'. flageUum, of which, 

 however, we have seen numerous authentic specimens in the Monaco 

 collection), we are fully convinced that nothing in the spiculation of these 

 types is of sufficient importance to be used as a generic character, so that it 

 is incumbent upon us to examine in detail the other features which have 

 been used as diagnostic. 



Branching. — Scirpearia is described as simple, Scirpearella as simple or 

 very feebly branched, and Ellisella as simple or dichotomously branched. 

 Now the question of branching, as has been already shown, is of no importance 

 in diagnosis. Specimens otherwise identical are described in this memoir, in 

 which one may be of great length and simple, another elongated and 

 bifurcating, while a third may be of no exceptional height and yet very 

 markedly branched. A very good example of this may be seen in Scirpearia 

 furcata. Contrast (1) the specimens from Mergui — (2) that orginally described 

 by Thomson and Henderson as Scirpearia, sp., and (3) the specimen from 

 Providence Island, all of which are included in this report. The very fact, 

 however, that a species of Scirpearia has been described in which branching 

 occurs shows the futility of relying upon this feature. 



Nature of the Verrucae. — The question of prominent or non- prominent 

 verrucae has already been discussed, and, as it has implicitly been abandoned 

 by most authors, need not occupy our time here ; but it is essential to pomt 

 out that the omission of this as a generic character almost finally necessitates 

 the abolition of the genus Ellisella. 



